Mask



FIG. 1 is a perspective view of a mask;

FIG. 2 is a front view of the mask;

FIG. 3 is a rear view of the mask;

FIG. 4 is a right side view of the mask;

FIG. 5 is a left side view of the mask;

FIG. 6 is a top view of the mask; and,

FIG. 7 is a bottom view of the mask.

The broken line showing of the canister of oxygen in FIG. 1 depicts environmental subject matter that forms no part of the claimed design. The broken lines in FIGS. 6 and 7 depict portions of the mask that form no part of the claimed design. 

CLAIM The ornamental design for a mask, as shown and described. 